John Veldhuis, ProSys
A few companies have leveraged Procedural Automation (also referred to as State Based Control) effectively on operating units. This will be more widespread as demands for better product transitions, handling of unit upsets and increased reliability in production facilities increases. Further to drive consistency and leveraging Procedural Automation, the ISA is releasing a new guideline “ISA106, Procedure Automation for Continuous Process Operations” which will be of interest to companies looking to benefit from their automation assets.
By automating what were previously manual procedures and incorporating them into the control system the following improvements can be made:
- Reduction in time to execute the procedure
- Elimination of mistakes or omitted steps when carrying out the procedure
- Improved outcome consistency and equipment reliability by using best practices
- Operations can focus on critical/high value units when upsets occur
Typical execution time reduction is between 5-30%. The value of efficiency and reliability gains are dependent on the specific process and need to be evaluated on a Unit basis.
In Larry O’Brien’s September 2010 ARC paper titled “Why We Need a Better Approach to Procedural Automation”, he states the following:
“In demand-limited industries like refining, the overarching objective is to improve utilization. This cannot be achieved without reducing unplanned downtime. Research shows that the largest reason for unscheduled downtime is operational or human error. This accounts for approximately 42 percent of the unscheduled shutdowns in the process industries. Of that 42 percent, 14 percent is directly related to procedural error. When researching the role of operators in the Refinery of the Future, several major operating companies concluded that they could address this by empowering a higher level of perspective on the entire production operation, one that enables flawless intervention by exception and relieves operators of manual tasks, freeing time for operators to perform more value-added activities.”¹
Specific improvements cited by our customers include reduction of incidents, faster start-ups and shutdowns, time saved using “safe park”, catalyst regeneration consistency and increased speed, faster and more consistent transitions, and conversion of disparate operations into Standard Work.
Incidents on Start-Up or Shutdown: Typical reduction opportunities are reflected in the comments of Scott Ostrowski and Kelly Kheim of ExxonMobil Chemicals:
“A disproportionate percentage of process safety incidents have occurred during transient operations, which include those conducted infrequently such as startups or shutdowns as well as abnormal or emergency events. A typical refining or petrochemical facility will spend less than 10% of its time in transient operations — yet 50+% of process safety incidents occur during these operations”.²
Process Knowledge: Additional benefits can be in the capturing of process knowledge and capturing that within the state based control. This is illustrated by Tom Nolan in his joint paper entitled " State Based Control and the Value Delivered from the Initial Design Through the Operating Life of the Facility”, AIChE, 2016.
“Loss of process knowledge through attrition is often an issue for those facilities that do not have a high level of automation or state based control. A large percentage of the work force is nearing retirement age. Within the next five years, about 20% of the workforce could retire.”…. “ This knowledge transfer has to happen before the experienced personnel retire.”³
Safe Park: Some customers have developed safe park states that allow a unit to idle in place at a safe, recycling, or reduced operational state for a short time. This gives operators time to return an upstream or downstream operation to its normal operation instead of shutting down the operation under control. Considerable time and intermediate product can generally be saved.
Catalyst Preparation or Regeneration: Catalyst preparation or regeneration is frequently very demanding. We have automated very complex preparations and regenerations to improve catalyst consistency and to reduce the time these take. One unit alone reduced its catalyst regeneration time by 15% while simultaneously improving catalyst consistency.
Transitions: A significant percentage of our customer’s requests for Procedural Automation derive from application to Units that operate in multiple modes or for different products for which transition material needs to be minimized. In these cases Procedural Automation is often coupled with sophisticated APC, non-linear, or model-based control systems. Simpler systems can be managed with transition tables. Customers typically report 10-18% reductions in transition times. Perhaps most importantly the best practice in these transitions is followed every time, simplifying the application of Standard Work (to use the Toyota nomenclature). A typical customer here is an ethylene furnace or other system that has a regular cycle of decoking or unit cycle.
Impact on Equipment Reliability: A significant percentage of equipment failures are related to operating outside the equipment’s intended design envelope, so-called “self-inflicted” equipment failure. Some of these excursions derive from inadequate procedure compliance, either because operators are very busy with more important matters, or because they are unaware of the equipment’s design limitations. In either case Procedural Automation can easily enforce design limits. Customers often overlook these benefits when considering Procedural Automation, but later report gains that cannot otherwise be explained.
Identifying companies that have good experience with your specific control system, your production units and specializing in state based control implementation will be key to success.
- Why We Need a Better Approach to Procedural Automation, Larry O'Brien [page 6]
- Tame Your Transient Operations, Scott W. Ostrowski and Kelly K. Keim, ExxonMobil Chemical Company
- State Based Control and the Value Delivered, Tom Nolan, ProSys